As the saying goes, "August 15th, Yun Zheyue, the 15th day of the first month, it snows, turn on the lights". What is the scientific truth of this sentence?

This sentence is a proverb summarized by ancient people according to some weather conditions in two seasons. Although people couldn't consider its correctness in ancient times, it was a conclusion drawn after years of observation, and its accuracy was relatively high. It should be said that it is a scientific proverb.

"On August 15th, Yun Zheyue, it snows and lights on the 15th day of the first month" reflects a meteorological activity in two festivals. It means that on the Mid-Autumn Festival on the fifteenth day of the eighth lunar month, if the moon is not visible in the sky at night, the clouds are thick or it is rainy directly, then in this case, it usually snows on the fifteenth day of the first month of the following year.

The corresponding situation of these two kinds of weather is a general conclusion that has been observed for many years in various places, and even from the current weather situation, it is accurate. For example, in 2006, the Mid-Autumn Festival began to be cloudy and the moon could not be seen. In 2007, it rained and snowed on the Lantern Festival on the fifteenth day of the first month, and it stopped snowing one day, which is in line with this proverb.

From the perspective of modern weather forecasting technology, "Yun Zheyue" and "Xueliang" are essentially two cold air activities that echo each other. In other words, if the phenomenon of "Yun Zheyue" appears on or around the Mid-Autumn Festival, it also indicates that cold air is coming. In this way, on the fifteenth day of the first month of the following year, cold air will invade again, forming a situation of "snow hits the lights". Therefore, the proverb "On August 15th, Yun Zheyue, it snows and lights on the 15th day of the first month" actually summarizes the activity law of cold air for about five months, and also provides a good guide for weather forecast.